1. Field of the Invention
The invention relates to a method for producing a topographical pattern on or in a papermachine fabric. It further relates to a corresponding papermachine fabric.
2. Discussion of Background Information
The use of rotary screen printing in the textile industry is well known. Typical examples of rotary screen printing are represented in the U.S. Pat. No. 2,511,511 (Murphy) and U.S. Pat. No. 3,420,167 (Van der Winden). Restrictions in the design and manufacture of rotary screens determine what fabric widths can be processed.
Rotary screens which are supplied by STORK NV are normally implemented in the configuration shown in FIG. 1. End or terminating rings 10, which have a larger diameter than the screens 12 themselves, provide the way by which the screen 12 is fixed and rotated on the machine. During the printing, the fabric has to be present in a width which permits it to run through between the two terminating rings 10 and which allows it direct contact with the screen 12. The actual application width 14 of a rotary screen is therefore always narrower than its entire “machine-width” dimension 16.
STORK NV supplies rotary screens in the following machine widths: 1410, 1750, 1980, 2650, 3050, 3500 and 3800 mm. SAXON SCREENS is a further manufacturer of rotary screens, the maximum available width of these screens being 2080 mm.
Fabrics which are used in the various sections of a paper machine can, however, have widths up to 10 m. Since this is the case, standard rotary screens cannot be used to transfer topographical features over the entire width of the papermachine fabric, specifically because of the screen configuration restrictions described above.
The manufacture of topographical fabrics for the production of decorative paper products is known. For example, U.S. Pat. No. 6,203,663 (Kamps) describes a method for the introduction of a decorative pattern onto a forming fabric by using stitching, stencil printing, printing or weaving techniques. The latter technique of weaving does not permit the production of complex topographical patterns and is more suited to “point patterning”, elevated fabric knuckles being used to produce small holes in the paper product. While complex topographical patterns can be achieved by using stitching techniques, the pattern is prone to deterioration as a result of the effects of abrasion. Stencil printing has similar problems to those which are associated with rotary screen printing in relation to the limited screen widths. In order therefore to transfer topographical features to wide papermachine fabrics by this method, it would be necessary for the fabric to be printed section by section over its entire width. The problems inherent in this method are that it is extremely time-consuming and it is necessary to position the stencil screen relative to a previously printed section in such a way that the topographical pattern is aligned and matched accordingly.
U.S. Pat. No. 4,529,480 (Trokhan) teaches a method for manufacturing a woven fabric which has a UV-cured polymer pattern network with deflection conduits. The pattern network and the deflection conduits extend over the entire width of the papermaking fabric width and are designated endless, since it is essentially one unbroken net-like pattern. However, because of restrictions of the process, the UV-cured pattern network has to be applied to the fabric in a batchwise manner or section by section. In addition, the application of a UV-cured section requires a number of different and defined steps, which have to be carried out successively. This particularly complex process has the disadvantages that it is both time-consuming and requires great attention to alignment and matching of the topographical pattern during the sectional application.